Elastomeric thermoplastics are well known in the art. For example, U.S. Pat. No. 3,758,643 teaches the preparation of such a blend by admixing a partially cured ethylene propylene copolymer or ethylene propylene terpolymer with polypropylene. Blends of monoolefin copolymer rubber, such as ethylene propylene copolymers having a high viscosity at low shear rate, with polyolefin resins, such as polypropylene are also known in the art. See U.S. Pat. No. 3,835,201.
Such elastomeric thermoplastic blends are used to produce molded or extruded articles, such as automotive decorative and structural parts, which required both the hot processing properties of a plastic and the cold mechanical properties of a vulcanized elastomer. It is also desirable that such articles be paintable. See U.S. Pat. No. 3,873,348 which discloses a paintable cured thermoplastic composition.
In order to achieve sufficient melt flow properties for processing, such elastomeric thermoplastics for molding and extruding purposes have generally been limited to low molecular weight materials obtained either directly through polymerization or indirectly through the breakdown of higher molecular weight materials during processing.
The present invention permits the use of high molecular weight elastomeric materials without polymer breakdown by incorporating therein a plasticizer such as a hydrocarbon oil. Processing as well as mechanical properties of the resulting blends have also been improved in the present invention by use of carbon black having high reinforcing capacity and low aggregate structure.